[Respiratory mechanics in animals. 2. The forced oscillation technique--review]

The analysis of respiratory mechanics using the forced oscillation technique (FOT) was originally developed for human medicine. Since this technique can be used during spontaneous breathing and does not require patient cooperation, it is generally applicable to conscious animals. In contrast to conventional methods to characterise the mechanics of breathing, FOT has the advantage of being non-invasive. Compared to the classical method which takes mechanical parameters (resistance, inertance, compliance) into account, the forced oscillation techniques utilises electrical parameters (resistance, inductance, capacitance). Briefly, in the forced oscillation technique, externally generated test signals are sent to the respiratory system under investigation. These test signals are superimposed on spontaneous breathing. In order to examine respiratory mechanics, the response of the respiratory system to these test signals is analysed and interpreted. The complex respiratory impedance resulting from this analysis contains information concerning the resistive, capacitive and inductive properties of the respiratory system. In general, FOT is a portable technique which can be applied to several kinds of animals.